Review: Hippocampal sclerosis in epilepsy: a neuropathology review

Hippocampal sclerosis (HS) is a common pathology encountered in mesial temporal lobe epilepsy (MTLE) as well as other epilepsy syndromes and in both surgical and post‐mortem practice. The 2013 International League Against Epilepsy (ILAE) classification segregates HS into typical (type 1) and atypical (type 2 and 3) groups, based on the histological patterns of subfield neuronal loss and gliosis. In addition, granule cell reorganization and alterations of interneuronal populations, neuropeptide fibre networks and mossy fibre sprouting are distinctive features of HS associated with epilepsies; they can be useful diagnostic aids to discriminate from other causes of HS, as well as highlighting potential mechanisms of hippocampal epileptogenesis. The cause of HS remains elusive and may be multifactorial; the contribution of febrile seizures, genetic susceptibility, inflammatory and neurodevelopmental factors are discussed. Post‐mortem based research in HS, as an addition to studies on surgical samples, has the added advantage of enabling the study of the wider network changes associated with HS, the long‐term effects of epilepsy on the pathology and associated comorbidities. It is likely that HS is heterogeneous in aspects of its cause, epileptogenetic mechanisms, network alterations and response to medical and surgical treatments. Future neuropathological studies will contribute to better recognition and understanding of these clinical and patho‐aetiological subtypes of HS.     

Neuroimaging of schizophrenia: structural abnormalities and pathophysiological implications

Schizophrenia, once considered a psychological malady devoid of any organic brain substrate, has been the focus of intense neuroimaging research. Findings reveal mild but generalized tissue loss as well as more selective focal loss. It is unclear whether these abnormalities reflect neurodevelopmental or neurodegenerative processes, or some combination of each; current evidence favors a preponderance of neurodevelopmental abnormalities. The pattern of brain abnormalities is also influenced by environmental and genetic risk factors, as well as by the course (and possibly even treatment) of this illness. These findings are described in this article.     

Impact of an optimized epilepsy surgery imaging protocol for focal epilepsy: A monocentric prospective study

Objective

To evaluate in a real clinical scenario the impact of the ILAE-recommended “Harmonized neuroimaging of epilepsy structural sequences”- HARNESS protocol in patients affected by focal epilepsy.

Methods

We prospectively enrolled focal epilepsy patients who underwent a structural brain MRI between 2020 and 2021 at Modena University Hospital. For all patients, MRIs were: (a) acquired according to the HARNESS-MRI protocol (H-MRI); (b) reviewed by the same neuroradiology team. MRI outcomes measures were: the number of positive (diagnostic) and negative MRI; the type of radiological diagnosis classified in: (1) Hippocampal Sclerosis; (2) Malformations of cortical development (MCD); (3) Vascular malformations; (4) Glial scars; (5) Low-grade epilepsy-associated tumors; (6) Dual pathology. For each patient we verified for previous MRI (without HARNESS protocol, noH-MRI) and the presence of clinical information in the MRI request form. Then the measured outcomes were reviewed and compared as appropriate.

Results

A total of 131 patients with H-MRI were included in the study. 100 patients out from this cohort had at least one previous noH-MRI scan. Of those, 92/100 were acquired at the same Hospital than H-MRI and 71/92 on a 3T scanner. The HARNESS protocol revealed 81 (62%) positive and 50 (38%) negative MRI, and MCD was the most common diagnosis (60%). Among the entire pool of 100 noH-MRI, 36 resulted positive with a significant difference (p < .001) compared to H-MRI. Similar findings were observed when accounting for the expert radiologists (H-MRI = 57 positive; noH-MRI = 33, p < .001) and the scanner field strength (H-MRI 43 = positive, noH-MRI = 23, p < .001), while clinical information were more present in H-MRI (p < .002).

Significance

The adoption of a standardized and optimized MRI acquisition protocol together with adequate clinical information contribute to identify a higher number of potentially epileptogenic lesions (especially FCD) thus impacting concretely on the clinical management of patients with focal epilepsy.     

MRI lesions masked by brain development: a case of infant-onset focal epilepsy

A 3-month-old male presented with right-side–dominant focal seizures. Focal spikes were observed on the left side of an electroencephalogram obtained at the time of onset. The immature development in the left middle temporal lobe was observed by initial magnetic resonance imaging (MRI). The hypoperfusion in the left temporal lobe observed with single-photon computed tomography was consistent with MRI findings. These MRI findings were not observed in a second MRI at 11 months of age. This observation may explain one of the causes of infant-onset focal epilepsy.     

Neuroimaging in epilepsy

Epilepsy is a common neurological disorder with diverse etiologies. Neuroimaging plays an important role in workup of patients with epilepsy. It helps to identify brain pathologies that require specific treatment; and also in formulating syndromic and etiological diagnoses so as to give patients and their relatives an accurate prognosis. Magnetic resonance imaging, specially the 3 tesla MRI is the imaging of choice because of its ability to detect small lesions like mesial temporal sclerosis, cortical dysplasias, small tumors, etc that are not detected by conventional MR or CT scan of brain. Identification of these lesions often helps in managing refractory epilepsies more effectively. However, cost and non-availability of MR in large part of the country necessitate the use of CT as an alternative. CT is often the initial investigation and also useful in acute situations. Functional imagings are used for pre-surgical work-up of refractory epilepsy cases with an aim to identify the epileptogenic focus and to delineate functional areas nearing the focus.     

Recommendations for the use of structural magnetic resonance imaging in the care of patients with epilepsy: A consensus report from the International League Against Epilepsy Neuroimaging Task Force

Structural magnetic resonance imaging (MRI) is of fundamental importance to the diagnosis and treatment of epilepsy, particularly when surgery is being considered. Despite previous recommendations and guidelines, practices for the use of MRI are variable worldwide and may not harness the full potential of recent technological advances for the benefit of people with epilepsy. The International League Against Epilepsy Diagnostic Methods Commission has thus charged the 2013‐2017 Neuroimaging Task Force to develop a set of recommendations addressing the following questions: (1) Who should have an MRI? (2) What are the minimum requirements for an MRI epilepsy protocol? (3) How should magnetic resonance (MR) images be evaluated? (4) How to optimize lesion detection? These recommendations target clinicians in established epilepsy centers and neurologists in general/district hospitals. They endorse routine structural imaging in new onset generalized and focal epilepsy alike and describe the range of situations when detailed assessment is indicated. The Neuroimaging Task Force identified a set of sequences, with three‐dimensional acquisitions at its core, the harmonized neuroimaging of epilepsy structural sequences—HARNESS‐MRI protocol. As these sequences are available on most MR scanners, the HARNESS‐MRI protocol is generalizable, regardless of the clinical setting and country. The Neuroimaging Task Force also endorses the use of computer‐aided image postprocessing methods to provide an objective account of an individual's brain anatomy and pathology. By discussing the breadth and depth of scope of MRI, this report emphasizes the unique role of this noninvasive investigation in the care of people with epilepsy.     

Juvenile myoclonic epilepsy – a generalized epilepsy syndrome?

Juvenile myoclonic epilepsy (JME) has been classified as a syndrome of idiopathic generalized epilepsy and is characterized by specific types of seizures, showing a lack of pathology using magnetic resonance imaging (MRI) and computed tomography scanning. However, JME is associated with a particular personality profile, and behavioral and neuropsychologic studies have suggested the possible involvement of frontal lobe dysfunction. The development of highly sensitive neuroimaging techniques has provided a means of elucidating the underlying mechanisms of JME. For example, positron emission tomography has demonstrated neurotransmitter changes in the cerebral cortex, quantitative MRI has revealed significant abnormalities of cortical gray matter in medial frontal areas, and ¹H-magnetic resonance spectroscopy has shown evidence of thalamic dysfunction, which appears to be progressive. Such techniques provide evidence of multi-focal disease mechanisms, suggesting that JME is a frontal lobe variant of a multi-regional, thalamocortical 'network' epilepsy, rather than a generalized epilepsy syndrome.     

Electrophysiological abnormalities in chronic epileptogenic foci: an intracellular study

Intracellular recordings were performed from chronic cobalt epileptogenic foci in rats. Two main features were found: (a) in 29% of the neurons, large depolarizations of long duration occurred coinciding with cortical surface paroxysms; and (b) in 13% of the neurons, partial spikes, whose amplitude varied little with membrane DC potential changes, occurred. It is suggested that these phenomena have a dendritic origin, and possible cellular mechanisms underlying the generation of paroxysmal events are discussed.     

功能性磁共振导航结合皮质电极描记切除功能区及其附近的癫痫灶

目的探讨利用fMRI导航结合皮质电极描记切除功能区及其附近癫痫灶的临床疗效。方法回顾性分析11例癫痫灶起源于功能区及其附近的癫痫病人的手术经验。病人术前发作频率（2．63±1．68）次／月。术前利用fMRI检查确定功能区位置并与导航图像进行融合,术中使用皮质电极描记标记出癫痫波的位置,通过导航系统了解功能区与癫痫波起源的关系。在保留功能区皮质的基础上,将病灶和癫痫波起源处皮质切除,而位于功能区皮质上的癫痫波起源处则给予小功率皮质热灼。结果皮质发育不全8例,灰质异位症2例,脑外伤后局部皮质软化1例。术后随访6～12个月,癫痫发作完全消失9例,术后3-6d内发作1次2例,随后未再出现癫痫发作。术后未出现明显的神经功能损害加重的情况。术后3个月复查脑电图显示基本正常。结论fMRI导航结合皮质电极描记切除起源于功能区及其附近的癫痫灶是一种微侵袭的手术方法,在切除癫痫灶的同时能最大限度地保留功能区的神经功能。     

Neuroimaging Characteristics of Pseudosubcortical Laminar Heterotopia

Subcortical laminar heterotopia (SLH) is a subtype of malformation of cortical development characterized by laminar gray matter between the cortex and ventricles, which can vary in thickness and may be continuous or discontinuous. The objective of this study is to describe a normal finding of high-resolution magnetic resonance imaging that may simulate an SLH. SLH is isointense to cortex on both T1- and T2-weighted/FLAIR images, usually both anteriorly and posteriorly in location. Conversely, pseudo-SLH is a normal variant present only at the posterior aspect of the brain, and with dark signal on both T1- and T2-weighted/FLAIR images.     

难治性癫癎MRJ颞极信号特点与癫癎的相关性分析

目的探讨难治性癫癎MRI颞极信号特点与致癎区相关性。方法回顾性分析339例难治性癫癎病人MRI颞极信号特点。根据癫癎发作起始区将研究对象分为颞叶癫癎、额叶癫癎、顶叶癫癎、枕叶癫癎、岛叶癫癎、多脑叶癫癎等6类。结果颞极信号异常187例,颞极信号异常侧别与致癎区侧别一致率达98．93％,颞极信号异常与癫癎类型或致癎区有关（χ2=311．339,P〈0．001）。与颞叶外癫癎比较,颢极信号异常更常见于颞叶癫癎。结论在各类癫癎中均可出现MR／颞极信号异常,但更常见于颞叶癫癎。颞极信号异常侧常与致癎区侧别一致．特别是颞叶癫癎。     

功能性磁共振和皮质脑电图在伴继发性癫(癎)脑肿瘤手术中的应用(附13例分析)

目的探讨术前功能磁共振成像（fMRI）和术中皮质脑电图（ECoG）在伴继发性癫疒间脑肿瘤手术中的应用价值。方法回顾性分析13例脑运动皮质区附近肿瘤病人的临床资料。术前通过fMRI了解相应脑功能区皮质和白质纤维束的形态和分布;术中在切除肿瘤前后行ECoG检测,确定致疒间灶的位置,指导肿瘤及致疒间灶的切除。结果手运动功能区受肿瘤推挤而出现功能转移或重组9例,行肿瘤全切除;功能区局部重叠2例,行肿瘤次全切除;大部分重叠2例,行肿瘤部分切除。ECoG确定的致疒间灶距肿瘤2 cm以内9例,3～5 cm 2例,与肿瘤重叠2例。术后出现短暂性失语1例,一过性偏瘫2例。结论fMRI能准确显示运动皮质中枢位置,对脑肿瘤术前手术方案制定和手术时减少重要功能区损伤具有重要意义。ECoG确定致疒间灶大多距肿瘤2 cm以内。     

Neuroimaging in epilepsy surgery: a review

In recent years there has been a shift away from invasive monitoring, with more emphasis on the role of neuroimaging, in the selection of patients for epilepsy surgery. Although video-EEG is essential to confirm the diagnosis, and to determine the ictal onset, neuroimaging, in particular magnetic resonance imaging (MRI), forms the basis for selection of most surgical candidates. MRI, using visual analysis, is able to detect hippocampal sclerosis, the most common cause of temporal lobe epilepsy, in the majority of patients with this condition, with quantitative MRI increasing the sensitivity of this imaging technique. Other lesions readily detected on MRI include dysplasia, neuronal migration disorders and cavernomas. Studies have shown that the best postoperative results are achieved in patients with a lesion visible on MRI. Functional imaging, both single photon emission computed tomography (SPECT), in particular ictal SPECT, and photon emission tomography (PET), are important ancillary investigations providing valuable corroborative evidence of a seizure focus.     

术中1.5T核磁共振外科治疗难治性癫癎

目的探讨应用术中1.5T核磁共振(MRI)治疗难治性癫癎的手术效果。方法手术治疗难治性癫癎15例,利用术中1.5T核磁共振,术前常规行T1、T2及T1加强,及弥散张量成像,术中切除(切开)后行T1、T2及T1加强及弥散张量成像检查,以确定切除范围及功能区定位,其中5例术中MR检查后扩大切除。结果左侧枕叶局灶性皮质发育异常2例,左侧颞叶海绵状血管瘤4例,左侧颞叶海马硬化1例,右侧额叶胚胎发育不良性神经上皮肿瘤1例,右侧中央前回局灶性皮质发育不良1例,右侧颞叶海马硬化1例,右侧颞叶海绵状血管瘤1例,右侧颞叶胶质瘤1级1例,右侧中央后回海绵状血管瘤1例,胼胝体切开2例,engle分级:Ⅰ级11例,Ⅱ级4例。结论术中1.5T核磁共振对切除(切开)病灶及功能保护有指导意义。     

Correlation between quantitative EEG and MRI in idiopathic generalized epilepsy

The objective of this study was to investigate the relationship between the focal discharges sometimes observed in the electroencephalogram of patients with idiopathic generalized epilepsies and subtle structural magnetic resonance imaging abnormalities. The main hypothesis to be assessed is that focal discharges may arise from areas of structural abnormality which can be detected by quantitative neuroimaging. Focal discharges were used for quantitative electroencephalogram source detection. Neuroimaging investigations consisted of voxel‐based morphometry and region of interest volumetry. For voxel‐based morphometry, volumetric MRI were acquired and processed. The images of each patient were individually compared with a control group. Statistical analysis was used to detect differences in gray matter volumes. Region of interest‐based morphometry was automatically performed and used essentially to confirm voxel‐based morphometry findings. The localization of the focal discharges on the electroencephalogram was compared to the neuroimaging results. Twenty‐two patients with idiopathic generalized epilepsies were evaluated. Gray matter abnormalities were detected by voxel‐based morphometry analysis in 77% of the patients. There was a good concordance between EEG source detection and voxel‐based morphometry. On average, the nearest voxels detected by these methods were 19 mm (mm) apart and the most statistically significant voxels were 34 mm apart. This study suggests that in some cases subtle gray matter abnormalities are associated with focal epileptiform discharges observed in the electroencephalograms of patients with idiopathic generalized epilepsies. Hum Brain Mapp, 2010. © 2010 Wiley‐Liss, Inc.     

The use of neuroimaging to study behavior in patients with epilepsy

Structural and functional neuroimaging continues to play an increasing role in the presurgical evaluation of patients with epilepsy. In addition to its value in localizing the epileptogenic zone and eloquent cortex, neuroimaging is contributing to our understanding of mood comorbidity in epilepsy. Although the vast majority of research has focused on patients with temporal lobe epilepsy (TLE), neuroimaging studies of patients with extratemporal epilepsy and primary generalized epilepsy are increasing in number. In this review, structural and functional imaging modalities that have received considerable research attention in recent years are reviewed, and their strengths and limitations for understanding behavior in epilepsy are assessed. In addition, advances in multimodal imaging are discussed along with their potential application to the presurgical evaluation of patients with seizure disorders.     

磁源性影像对颞叶癫(癎)定位的临床价值

目的探讨磁源性影像（MSI）对颞叶癫癎患者癫癎灶的定位价值。方法23例颞叶癫癎的患者进行了MSI检查,将结果与普通EEG、视频EEG和皮质EEG结果进行比较。其中8例行手术治疗,5例行伽玛刀治疗。结果23例患者中MEG显示单致癎灶15例,多致癎灶8例,MEG于V-EEG的符合率为84.6%,17例MRI检查异常,MEG与MRI结果符合率76.4%。8例术中ECoG定位检查,与MEG定侧定位均完全符合。13例患者MEG定位后行手术或伽玛刀治疗,疗效满意。结论MSI对颞叶癫癎定位准确,具有指导临床进一步治疗的价值。     

弥散张量成像在继发全面性发作癫痫患者中的应用研究

目的 评价弥散张量成像(DTI)对于常规MRI未发现病灶的部分性继发全面性发作癫痫患者的病灶检出能力.方法 使用Siemens 3.0T磁共振成像系统对30例成年继发全面性发作癫痫患者和30例正常对照者进行扫描,得到弥散加权成像,采用基于体素的分析方法对癫痫患者和正常对照组的数据进行分析.结果 癫痫组右侧梭状回和楔前叶、右侧额内侧回和钩回、左侧扣带回、左侧颞下回、左侧小脑扁桃体和左侧中央前回的脑区FA值较正常对照组降低,差异有统计学意义(P＜0.001);癫痫组右侧海马旁回、右侧颞下回、右侧胼胝体、右侧额内侧回、右侧额下回、扣带回、右侧前扣带回、右侧舌回、右侧梭状回和枕中回,左侧颞中回、左侧钩回和左侧中央前回的脑区ADC值较正常对照组升高,差异具有统计学意义(P＜0.001);左侧直回的脑区ADC值较正常对照组降低,差异具有统计学意义(P＜0.001).结论 DTI检查可发现常规MRI检查为阴性的部分性继发全面性发作癫痫患者存在的广泛脑白质微结构异常.